The present invention relates generally to high temperature vessels having a refractory lining and, more particularly, to structure for retaining the refractory lining in place in such a vessel.
High temperature vessels of the type to which the present invention relates include ladles for containing molten metal, tilting furnaces, rotary kilns, or any other vessel lined with a refractory material and having a curved interior cross-section. Such a vessel typically includes a metal outer shell, an inner lining composed of a plurality of aligned or superimposed courses of refractory brick and an opening at one end of the vessel. In the absence of structure at the open end for retaining the refractory bricks in place, a force exerted on the refractory bricks, in a direction toward the vessel's open end, could cause one or more courses of refractory bricks to fall out at the open end. This could occur, for example, if a ladle were tilted so that the open end was totally or substantially inverted, as when a ladle is tilted to empty it of residual slag or the like. In such a case, the weight of the inverted lining, itself, would be enough to cause refractory bricks to fall out.
Various structures have been employed in the past to retain the refractory lining in place, but all of these prior art structures have had drawbacks or defects. One such prior art retaining structure was in the form of a steel angle iron having one flange attached to the inner surface of the ladle's outer shell, adjacent the ladle's open end, and another flange, unenclosed by refractory material, extending from its junction with the one flange, at the ladle's open end. This other flange extended radially inwardly, with respect to the ladle interior, a distance substantially the same as that to which the refractory material extended, and there was a layer of refractory ramming material sandwiched between the nearest course of refractory brick and one surface of the inwardly extending flange of the steel angle iron. When the ladle was wholly or substantially inverted, the aligned courses of refractory brick were supported by the inwardly extending flange of the steel angle iron, and this prevented the refractory material from falling out of the inverted ladle.
A problem arose when a ladle having this type of retaining structure was subjected to preheating. During preheating, a preheater having a cross-sectional area substantially the same as the cross-sectional area of the ladle directly faced the open end of the ladle, adjacent thereto, and hot gases were directed from the preheater through the open end into the interior of the ladle. All hot exhaust gases escaping from the interior of the ladle during the preheating operation flowed out of the ladle adjacent the retaining structure, and because the inwardly extending flange of the angle iron was not enclosed by refractory, that flange was heated by the hot exhaust gases flowing adjacent the flange, eventually causing that flange to buckle. Buckling interfered with the ability of the angle iron to perform its intended retaining function with respect to the refractory lining when the vessel was inverted.
In an attempt to solve the problem described in the preceding paragraph, the angle iron was turned around so that the inwardly extending flange of the angle iron abutted the nearest course of refractory brick, and the entire angle iron was covered with a layer of refractory ramming material, reinforced with so called "crows foot" elements. However, this embodiment also presented problems. The refractory ramming material was exposed to wear, thereby requiring more frequent maintenance on the ramming material.
In addition, during those instances when the courses of refractory brick had to be removed, for periodic relining of the ladle, the inwardly extending flange of the angle iron was located directly in the path of the jackhammer normally employed to remove the courses of refractory brick. The jackhammer normally extends into the ladle through the ladle's open end along a line substantially parallel to the center line of the ladle, and the jackhammer removes the courses of refractory brick, starting with the course nearest the open end and proceeding toward the other end of the ladle. When the inwardly extending flange of the angle iron retaining member is disposed in the manner described in the preceding paragraph, there is an increased likelihood that the angle iron will be damaged by the jackhammer, and the angle iron will require more frequent replacement.